01 Laws of motion - Target Publications€¦ · STD. IX Science and Technology Printed at: ... 9....

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© Target Publications Pvt. Ltd. No part of this book may be reproduced or transmitted in any form or by any means, C.D. ROM/Audio Video Cassettes or electronic, mechanical

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STD. IX Science and Technology

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Written as per the latest syllabus prescribed by the Maharashtra State Bureau of Textbook Production and Curriculum Research, Pune.

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• Exhaustive coverage of entire syllabus.

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While designing the book, our main intention was to create a book that would act as a single point of reference for students. We wanted this book to provide students, the much needed answers for their textual questions as well as build up their knowledge quotient in the process.

Science and Technology: Std. IX has been prepared as per the new syllabus and paper pattern which is more child-centric and focuses on active learning along-with making the process of education more enjoyable and interesting.

We have infused the book with a liberal sprinkling of real life examples, pictorial explanations and additional questions. Questions titled under 'Use your brain power', 'Can you tell' and a series of 'In-text Questions', pave the way for a robust concept building.

Every chapter begins with covering all the textual content in the format of Objectives, Question - Answers, Give Reasons, Numericals, Diagram-based questions, paragraph based questions and a host of other Objective and Subjective type of questions. The chapter also includes Activity Based Questions that explain certain concepts to students in a point wise manner through the medium of an activity. Wherever possible questions are allotted with marks in accordance with new marking scheme. The question without marks can be modified as per the new marking scheme and asked in examination. Memory maps have been included wherever needed which provides a quick revision of the important topics of a chapter. The chapter eventually ends with a Chapter wise Assessment that stands as a testimony to the fact that the child has understood the chapter thoroughly.

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ContentsNo. Topic Name Page No. 1. Laws of Motion 1 2. Work and Energy 29 3. Current Electricity 51 4. Measurement of Matter 70 5. Acids, Bases and Salts 96 6. Classification of Plants 121 7. Energy Flow in an Ecosystem 133 8. Useful and Harmful Microbes 147 9. Environmental Management 160

10. Information Communication Technology (ICT) 175 11. Reflection of Light 185 12. Study of Sound 207 13. Carbon : An Important Element 224 14. Substances in Common Use 242 15. Life Processes in Living Organisms 264 16. Heredity and Variation 285 17. Introduction to Biotechnology 303 18. Observing Space : Telescopes 322

Note: Textual exercise questions are represented by * mark.

Textual solved examples are represented by + mark.

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; *1. Select the proper option and complete the

statements: [1 Mark each] (single, all, double, ionic, carbon, give and take,

hydrogen, multiple, share, most, covalent) i. A carbon atom forms a _______ bond with

other atoms. In this bond, the two atoms _______ electrons.

ii. All the carbon bonds in a saturated hydrocarbon _______ electrons.

iii. At least one carbon bond in an unsaturated hydrocarbon is _______.

iv. _______ is the essential element in all the organic compounds.

v. The element hydrogen is present in _______ of the organic compounds.

Answers: i. covalent, share ii. share iii. multiple iv. Carbon v. most 2. Fill in the blanks: [1 Mark each] i. Graphite can be used for writing on paper

because of its _______ structure. ii. _______ form of coal contains less than 60%

of carbon. iii. Methane is obtained from natural gas by ______. Answers: i. layered ii. Peat iii. fractional distillation 3. Select the appropriate options and complete

the following paragraph. [3 Marks] (amorphous, crystalline, three, four, six,

diamond, graphite, fullerene) Allotropy is the phenomenon in which an

element exists in different physical forms having different physical properties but similar chemical properties. Carbon occurs in several allotropic forms. Diamond, graphite and fullerenes are _______ allotropes of carbon. In _______, each carbon atom is bonded to _______ neighbouring atoms by covalent bonds forming a tetragonal three-dimensional structure. In _______, each carbon atom is bonded to _______ neighbouring atoms by covalent bonds forming a hexagonal layered structure. _______ molecules are found in the form of buckyballs and buckytubes.

Answer: Allotropy is the phenomenon in which an

element exists in different physical forms having different physical properties but similar chemical properties. Carbon occurs in several allotropic forms. Diamond, graphite and fullerenes are crystalline allotropes of carbon. In diamond, each carbon atom is bonded to four neighbouring atoms by covalent bonds forming a tetragonal three-dimensional structure. In graphite, each carbon atom is bonded to three neighbouring atoms by covalent bonds forming a hexagonal layered structure. Fullerene molecules are found in the form of buckyballs and buckytubes.

1. The lead used in pencil is made by mixing

_______. (A) graphite with glass (B) graphite with clay (C) diamond with clay (D) coal with coke 2. The first example of fullerene is _______. (A) C60 (B) C70 (C) C82 (D) C86 3. When a mixture of hydrogen and carbon

monoxide gases are heated at 300C in the presence of _______ catalyst, methane gas is produced.

(A) iron (B) copper (C) coke (D) nickel Answers: 1. (B) 2. (A) 3. (D) MCQs based on practicals / activities 1. When carbon dioxide dissolves in water,

_______ is formed. (A) hydrogen (B) carbonic acid (C) acetic acid (D) oxygen 2. When limestone was treated with dilute HCl, a

gas was produced. Which of the following is correct regarding the gas?

(A) It is brown in colour. (B) It is basic in nature. (C) It is odourless. (D) It supports combustion.

Carbon: An Important Element13Fill in the blanks

Choose the correct alternative [1 Mark each]

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Chapter 13: Carbon: An Important Element

3. On adding universal indicator solution to a gas jar filled with CO2, the colour of the solution changes to _______.

(A) blue (B) green (C) violet (D) yellow Answers: 1. (B) 2. (C) 3. (D) 1. Fullerenes are insoluble in organic solvents. 2. The purest form of coal is called charcoal. 3. Carbon dioxide is used for the preparation of

washing soda. Answers: 1. Wrong Fullerenes are soluble in organic solvents. 2. Wrong The purest form of coal is called anthracite. 3. Right 1. Graphite, Coke, Buckyball, Diamond 2. Ethane, Propane, Ethene, Methane 3. Charcoal, Anthracite, Lignite, Peat Answers: 1. Coke Coke is an amorphous form of carbon while

others are crystalline forms of carbon. 2. Ethene Ethene is an unsaturated hydrocarbon while

others are saturated hydrocarbons. 3. Charcoal Charcoal is not a type of coal while others are

different types of coal. 1. Bituminous coal : 70-90% carbon :: _______ :

95% carbon. 2. Coal : Amorphous form of carbon :: Fullerene

: _______. Answers: 1. Anthracite Bituminous coal contains 70-90% carbon and

anthracite contains 95% carbon. 2. Crystalline form of carbon Coal is an amorphous form of carbon and

fullerene is a crystalline form of carbon.

1. Match the hydrocarbons given in Group

‘A’ with their respective chemical formulae given in Group ‘B’. Group ‘A’ Group ‘B’ i. Ethane a. CH CH ii. Propene b. CH3 CH2 – CH3iii. Ethyne c. CH3 – CH3 iv. Propane d. CH3 – CH = CH2

Answer: (i – c), (ii – d), (iii – a), (iv – b) 1. Can you recall? (Textbook page no. 138) i. What is an element? What are the different

types of elements? [2 Marks] Ans: Substance whose molecules are made up of one

or more identical atoms is called an element. Elements are generally classified into three

groups: a. Metals: E.g.: gold, silver, copper, tin, etc. b. Non-metals: E.g.: carbon, sulphur, phosphorus, etc. c. Metalloids: E.g.: Silicon, germanium, etc. ii. What remains behind on complete

combustion of any organic compound? [1 Mark]

Ans: a. Any organic compound on complete combustion produces carbon dioxide (CO2) and water (H2O).

b. However, in limited supply of air, organic compounds undergo incomplete combustion and a black substance (carbon black) remains behind.

iii. What type of element is carbon? Give some

information about it. [3 Marks] Ans: Carbon is a non-metallic element. a. Carbon is found in nature in free state as

diamond and graphite. b. It is also found in the combined state in

the form of compounds such as: petroleum, natural gas, carbon dioxide, etc.

c. Its chemical symbol is C. d. Its atomic number is 6 and atomic mass

is 12 u. e. Electron configuration is (2, 4). f. Its valency is 4. g. It exhibits allotropy. h. It forms the basis of organic compounds

(hydrocarbons).

Answer the following

Odd one out [1 Mark each]

Right or Wrong. If wrong, write the correct sentence

[1 Mark each]

Complete the analogy [1 Mark each]

Match the following [½ Mark each]


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Std. IX: Science and Technology

2. Can you tell? (Textbook page no. 138) What is a compound? How are compounds

formed? [2 Marks] Ans: i. A compound is the substance that is

composed of two or more different elements.

E.g.: sugar, water, ammonia, carbon dioxide, etc.

ii. Compounds are formed by the chemical combination of two or more different chemical elements in such a way that the atoms of the different elements are held together by chemical bonds that are difficult to break.

E.g.: Pure water is a compound made from two elements-hydrogen and oxygen.

*3. In which compound forms does carbon

occur? [2 Marks] Ans: Carbon occurs in the combined state in the

following compounds: i. As carbon dioxide and in the form of

carbonates such as calcium carbonate, marble, calamine (ZnCO3), etc.

ii. Fossil fuels – coal, petroleum, natural gas. iii. Carbonaceous nutrients – carbohydrates,

proteins, fats. iv. Natural fibres – cotton, wool, silk. *4. Explain: Petrol, diesel, coal are fossil fuels.

[2 Marks] Ans: i. Fossil fuels are formed from plants,

animals and other creatures that died millions of years ago and got buried under the earth.

ii. Their remains gradually changed over the years due to heat and pressure in the earth’s crust forming coal, oil (petrol, diesel) and natural gas.

iii. These substances release energy when burnt and are used as fuels.

Hence, petrol, diesel, coal are fossil fuels. 5. What is allotropy? [2 Marks] Ans: Elements occurring in more than one form

wherein the chemical properties of these different forms are the same but their physical properties are different is called allotropy.

E.g.: Carbon exists in crystalline forms like diamond, graphite, etc. and in amorphous forms like coal, coke, etc.

6. Explain the structure of diamond in brief. [3 Marks]

Ans: Structure of diamond: i. In diamond, each carbon atom is bonded

to four other neighbouring carbon atoms by covalent bonds.

ii. Such a pattern is repeated in the entire crystal structure resulting in a giant molecule.

iii. Therefore, diamond has a tetragonal three-dimensional structure, which makes it very hard.

7. Give the properties of diamond. [2 Marks] Ans: Properties of diamond: i. Pure diamond is the hardest known

natural substance. ii. Diamond exhibits great lustre and

brilliance, which gives it a shiny, freshly polished look.

iii. Its melting point is 3500 C. iv. Its density is 3.5 g/cm3. v. It is a bad conductor of electricity as it

does not have free electrons. vi. It does not dissolve in any solvent and is

resistant to acids and bases. vii. When diamond is heated at 800 C in

the presence of oxygen, only CO2 is formed.

8. Discuss the structure of graphite. [3 Marks] Ans: Structure of graphite: i. In graphite, each carbon atom is bonded

to three other neighbouring carbon atoms by covalent bonds so that a hexagonal layered structure is formed.

ii. Each graphite crystal is made up of many sheets or layers of carbon atoms.

iii. One layer of graphite is called graphene. iv. These layers slip over each other on

applying pressure making graphite very soft and slippery.

Structure of carbon atoms in diamond

Carbon

Structure of carbon atoms in graphite

Carbon


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9. Give the properties of graphite. [2 Marks] Ans: Properties of graphite: i. Graphite found in nature is black, soft,

brittle and slippery. ii. Inside each layer of graphite, free

electrons move continuously within the entire layer. Hence, graphite is a good conductor of electricity.

iii. Due to its layered structure, graphite can be used for writing on paper.

iv. Graphite does not dissolve in most of the solvents.

v. It has density of 1.9 to 2.3 g/cm3. *10. How will you prove experimentally that

graphite is good conductor of electricity? [5 Marks]

Ans: i. Aim: To prove that graphite conducts electricity.

ii. Apparatus: Lead pencil, battery/cell, small bulb, electrical wires.

iii. Procedure: a. Sharpen a lead pencil from both its

ends. b. Now, connect both the sharpened ends

using electrical wires, one end to a cell/battery and the other end to a small bulb which in turn is connected to the other end of the cell/battery.

c. Start the electric current in the circuit and observe.

iv. Diagram: v. Observation: The electric bulb in the

circuit glows. vi. Inference: This experiment shows that

graphite (present in pencil lead) is a good conductor of electricity.

*11. Explain: Diamond, graphite and fullerenes

are crystalline forms of carbon. [3 Marks] Ans: i. Crystalline forms of a substance have

a regular and definite arrangement of atoms. They have a definite geometrical shape, sharp edges and plane surfaces.

ii. In diamond, each carbon atom is covalently bonded to four other neighbouring carbon atoms to form a tetragonal three dimensional structure. Thus, diamond has a regular and definite arrangement of atoms.

iii. In graphite, each carbon atom is covalently bonded to three other neighbouring carbon atoms to form a hexagonal layered structure. Thus, graphite has a regular and definite arrangement of atoms.

iv. Fullerene molecules are found in the form of buckyballs (spherical) and buckytubes (cylindrical). A molecule of fullerene consists of 30 to 900 carbon atoms. Thus, fullerenes have a regular and definite arrangement of atoms.

Hence, diamond, graphite and fullerenes are crystalline forms of carbon.

*12. Classify carbon. [2 Marks] Ans: i. Carbon is classified into two types: a. Crystalline forms and b. Non-crystalline/amorphous forms. ii. The crystalline forms of carbon are

further classified into three types: a. Diamond b. Graphite c. Fullerenes iii. The amorphous forms of carbon are

further classified into following types: a. Coal: It is of four types. They are peat, lignite, bituminous

coal and anthracite. b. Charcoal c. Coke *13. What are the different types of coal? What

are their uses? [5 Marks] Ans: The different types of coal are: Peat, lignite, bituminous coal and anthracite. i. Peat: a. Peat formation is the first step in

the formation of coal. b. It is a brown material consisting of

partly decomposed organic matter. c. It contains a high proportion of

water and less than 60% of carbon. Uses: Dry form of peat can be used as fuel. ii. Lignite: a. Lignite formation is the second

step in the formation of coal. b. It is also referred to as brown coal. c. It is formed from peat due to

increased pressure and temperature inside the earth.

d. It has a carbon content of around 60-70%.

Flow of electric currentthrough graphite

Pencil

Bulb

Cell


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Uses: a. Lignite is used exclusively as a

fuel for steam-electric power generation.

b. It can also be used as an alternative to chemical pesticides.

iii. Bituminous coal: a. Bituminous coal is formed in the

third step in the formation of coal. b. It is a relatively soft coal

containing tar-like substances called bitumen and is often referred to as black coal.

c. It is usually formed as a result of high pressure being exerted on lignite.

d. It has a carbon content of around 70-90%.

e. It is of higher quality than lignite. Uses: a. It is used as a fuel to produce

steam that runs train locomotives. b. It was previously used as a

domestic fuel. iv. Anthracite: a. It is a hard, compact variety of

coal and is known as the pure form of coal.

b. It contains about 95% of carbon. Uses: It is used in metal smelting and

fabrication industries. 14. What is the difference between lignite and

anthracite based on the percentage of carbon? [1 Mark]

Ans: Lignite contains 60-70% of carbon while anthracite contains about 95% of carbon.

15. Write a short note on charcoal. [2 Marks] Ans: i. Charcoal is formed by the combustion

of wood, bones, horns, etc., in an insufficient supply of air.

ii. It is a light weight, black, amorphous form of carbon.

iii. It is highly porous and brittle material. iv. It is a bad conductor of heat and

electricity. *16. Write two physical properties each of: i. Diamond ii. Charcoal iii. Fullerene [3 Marks] Ans: i. Physical properties of diamond: Refer Answer the following: Q.7. i. to v. ii. Physical properties of charcoal: Refer Answer the following: Q.15. ii. to iv.

iii. Physical properties of fullerenes: a. It is a crystalline allotrope of

carbon which is found in the form of buckyballs and buckytubes.

b. Fullerenes are soluble in organic solvents such as carbon disulphide, chlorobenzene, etc.

c. At a particular temperature, fullerenes act as superconductor.

17. What is coke? [1 Mark] Ans: The non-crystalline form of carbon that

remains when coal gas is removed from coal is called coke.

*18. Explain: Uses of various allotropes of

carbon. [5 Marks] Ans: Uses of various allotropes of carbon such as

diamond, graphite, fullerenes, coal and coke are as follows:

i. Uses of diamond: a. Diamonds are used in glass

cutting and rock drilling machines.

b. Diamonds are used as a precious stone in jewellery.

c. Diamond knives are used in the eye surgery.

d. Diamond dust is used for polishing other diamonds.

e. Diamond is used to make windows giving protection from radiation in space and in artificial satellites.

ii. Uses of graphite: a. Graphite is used for making

lubricants. b. It is used for making carbon

electrodes. c. It is used in pencils for writing. d. It is used in paints and polish. e. It is used in arc lamps, which give

a very bright light. iii. Uses of fullerenes: a. Fullerenes are used as insulators. b. Fullerenes are used as a catalyst

in water purification. c. At a particular temperature, fullerene

exhibits superconductivity. iv. Uses of coal: a. Coal is used as fuel in factories

and homes. b. It is used to obtain coke, coal gas

and coal tar. c. It is used in thermal power plants

for generation of electricity. v. Uses of coke: a. Coke is used as domestic fuel. b. It is used as a reducing agent.


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c. It is used in the production of water gas (CO + H2) and producer gas (CO + H2 + CO2 + N2).

*19. Write the uses of diamond. [2 Marks] Ans: Refer Answer the following: Q.18.i. *20. Why are carbon and its compounds used as

fuels? [2 Marks] Ans: i. Most of the carbon compounds give a

lot of heat and light when burnt in air. ii. Saturated hydrocarbons undergo complete

combustion to form CO2 and H2O and no smoke is produced.

Hence, carbon and its compounds are used as fuels.

21. What are covalent compounds? Enlist their

properties. [2 Marks] Ans: Covalent compounds: Covalent compounds are formed when two or

more atoms bond by sharing the valence electrons.

E.g.: Methane (CH4) Properties of covalent compounds: i. Covalent compounds have low melting

points and boiling points. ii. Generally, they are insoluble in water

and soluble in organic solvents. iii. They are poor conductors of heat and

electricity. 22. Draw the structural formula of methane.

[1 Mark] Ans: Structural formula of methane: 23. Define saturated hydrocarbons. [2 Marks] Ans: The hydrocarbons, which have only single

bonds between carbon atoms, are called saturated hydrocarbons.

E.g.: Ethane (CH3 CH3), Propane (CH3 CH2 CH3), etc. 24. What are unsaturated hydrocarbons?

[2 Marks] Ans: The hydrocarbons having at least one multiple

bond (can be a double or a triple bond) between carbon atoms are called unsaturated hydrocarbons.

E.g.: Ethene (CH2 = CH2), Ethyne (CH CH), Propene (CH3 CH = CH2), Propyne (CH3 C CH)

25. Use your brain power! (Textbook page no. 143) Does an electric charge form on atoms

when a covalent bond is formed between them? Why is a single bond between two carbon atoms strong and stable?

[2 Marks] Ans: i. No, there is no electric charge on atoms

when a covalent bond is formed in between them.

ii. A carbon-carbon single bond is a covalent bond formed by mutual sharing of two electrons, one from each of the two atoms. As the electron pair is shared amongst the two atoms, the carbon-carbon single bond is strong and stable.

*26. Explain the properties of carbon.

[2 Marks] Ans: Properties of carbon: i. Carbon is a soft, grey or black

non-metal. ii. Carbon is found in air as carbon dioxide

as also in fuels like biogas, petroleum and marsh gas.

iii. Elemental carbon is an inert substance, insoluble in water, acids, bases and organic solvents.

iv. It forms covalent bonds with other carbon atoms or with atoms of other elements.

v. Carbon exists in nature in more than one form i.e. it exhibits allotropy.

For example: The crystalline forms of carbon are diamond, graphite and fullerene.

The non-crystalline forms of carbon are coal, coke, charcoal, etc.

vi. On ignition, carbon reacts with oxygen in the air to form carbon dioxide (CO2).

27. Discuss in brief the occurrence of carbon

dioxide. [2 Marks] Ans: Occurrence of carbon dioxide: i. Carbon dioxide (CO2) occurs in air in

the free state at a concentration of about 0.03% by volume.

ii. Exhaled air contains about 4% of CO2. iii. CO2 is the principal gas produced by the

combustion of wood, other organic materials, fossil fuels such as coal, petroleum, natural gas, etc.

iv. CO2 is present as a salt in chalk and Shahabad tiles/marble/limestone.

C

H

H

H H


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*28. How will you verify the properties of carbon dioxide? [5 Marks]

Ans: The properties of carbon dioxide can be verified by carrying out the reaction between calcium carbonate (CaCO3) and hydrochloric acid (HCl).

The chemical equation for the reaction is as follows:

CO2 obtained in the above reaction is tested

for different properties: i. Colour: It is found to be colourless. ii. Odour: It is found to be odourless. iii. On pouring some limewater into a jar

containing CO2, it turns milky white, which indicates the formation of insoluble calcium carbonate precipitate.

iv. On placing a burning candle in a jar

containing CO2, the flame extinguishes. This indicates that CO2 neither burns nor supports combustion.

v. On testing with universal indicator solution, yellow or orange colour is obtained. This shows that CO2 is a weak acid with pH in the range of 3-6.

vi. On pouring some amount of water into a jar containing CO2, carbonic acid (H2CO3) is formed due to its solubility in water.

vii. On dropping a moist blue and red litmus paper into a jar containing CO2, the blue litmus paper turns red while the red litmus paper remains as it is. This shows that CO2 is acidic in nature.

29. Use your brain power! (Textbook page no. 145) Is the density of CO2 more or less than that

of air? [1 Mark] Ans: CO2 is denser than air. Density of CO2 is

1.97 g/cm3, which is about 1.67 times more than that of air.

*30. Explain: Practical uses of CO2. [2 Marks] Ans: Practical uses of CO2 are: i. CO2 is used to make aerated drinks. ii. CO2 under pressure, is used in fire

extinguishers. iii. Liquefied CO2 is used as a solvent for

dry cleaning.

iv. Solid CO2 is used in cold storage to keep milk, milk products and other frozen substances cool during transport.

v. Liquified CO2 is used to remove caffeine from coffee.

vi. It is also used for getting special effects of a mist in dramas and movies.

31. Explain the working of a regular CO2 based

fire extinguisher. [5 Marks] Ans: The working of a regular CO2 based fire

extinguisher can be explained as follows: i. A fire extinguisher contains sodium

bicarbonate powder. ii. There is also dilute sulphuric acid

placed in a glass capsule. iii. When the capsule breaks on pressing the

knob, the sulphuric acid comes in contact with the sodium bicarbonate and the two react chemically to release CO2 which comes out.

iv. The chemical reaction can be shown as,

v. Fires need oxygen, fuel and heat to

ignite and removing any one of those three components can put out a fire.

vi. Carbon dioxide (CO2) based fire extinguishers prove effective because CO2 molecules are heavier than oxygen molecules and thus, they push out oxygen surrounding the fire, extinguishing the blaze.

vii. In addition, CO2 based fire extinguishers do not cause corrosion and are non-conductors of electricity.

viii. Therefore, these are generally used when electrical and electronic equipment catches fire.

Ca(OH)2 (aq) + CO2 (g) CaCO3(s) + H2O(l)

Limewater Calcium carbonate

Water Carbon dioxide 2NaHCO3 + H2SO4 Na2SO4 + 2H2O + 2CO2

Dilute sulphuric

acid

Sodium sulphate

Sodium bicarbonate

Water Carbondioxide

Internal structure of a fire extinguisher

The knob

Capsule

Sulphuricacid

Powder of sodium bicarbonate

CaCO3 + 2HCl CaCl2 + H2O + CO2 Calcium carbonate

Hydrochloric acid

Calcium chloride

Water Carbon dioxide


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*32. Explain: Use of CO2 in fire extinguisher. [2 Marks]

Ans: i. CO2 does not support combustion and it is non-poisonous.

ii. CO2 molecules are heavier than oxygen molecules and thus, they push out oxygen surrounding the fire, extinguishing the blaze.

iii. In addition, CO2 does not cause corrosion and is a non-conductor of electricity.

iv. Therefore, CO2 based fire extinguishers are generally used when electrical and electronic equipment catches fire.

33. Write a short note on the occurrence of

methane. [2 Marks] Ans: Occurrence of methane: i. Methane is the major component of

natural gas, about 87% by volume. ii. Decomposition of organic matter in the

absence of air (anaerobic condition) produces methane. Hence, it is produced in a biogas production plant.

iii. It is found in coal mines. iv. Methane is found at the surface of

marshy places and hence it is also called as marsh gas.

v. On heating a mixture of hydrogen and carbon monoxide gases at 300 C in the presence of nickel (catalyst), methane gas is formed.

vi. Fractional distillation of natural gas gives methane in its pure form.

*34. Explain: Methane is called marsh gas.

[2 Marks] Ans: i. Methane is produced when vegetation

decomposes naturally in marshes and swamps by anaerobic digestion.

ii. As methane is found at the surface of such marshy places, it is also called as marsh gas.

35. State the physical properties of methane.

[2 Marks] Ans: Physical properties of methane: i. Methane is a colourless gas at room

temperature. ii. The melting point of methane is

182.5 C iii. Its boiling point is 161.5 C. iv. The density of liquid methane is less

than that of water. v. Methane is sparingly soluble in water

but highly soluble in organic solvents like gasoline, ether and alcohol.

36. State the uses of methane. [2 Marks] Ans: Uses of methane: i. Methane in the form of natural gas is

used in industries such as fabric mills, paper mills, food processing industry, petrol purification, etc.

ii. Being the smallest hydrocarbon, the proportion of CO2 released in the combustion of methane is small and, therefore, it is used as a domestic fuel.

iii. Methane is used for the production of many organic compounds such as ethanol, methyl chloride, methylene chloride and acetylene.

iv. Methane is used for electricity generation by burning it as a fuel in a gas turbine or steam generator.

37. What is biogas? [2 Marks] Ans: Biogas: i. Biogas typically refers to a mixture of

different gases produced by the breakdown of organic matter in the absence of oxygen (anaerobic condition).

ii. Organic matter includes agricultural waste, animal dung, dry leaves, wet garbage, manure, food waste, etc. which get decomposed by anaerobic microbes in a biogas plant.

iii. Biogas primarily contains methane (CH4) (about 55-60%) and carbon dioxide (CO2) and small amounts of hydrogen sulphide (H2S), moisture, etc.

iv. The gases methane, hydrogen and carbon monoxide (CO) can react with oxygen, which releases large amount of energy. This allows biogas to be used as a fuel.

38. Give the uses of biogas. [2 Marks] Ans: Uses of biogas: i. Biogas is a very cheap fuel option,

which also meets the demand for cooking gas.

ii. Biogas is used for production of electricity.

iii. Biogas can be compressed and used to power motor vehicles.

iv. In addition, a very good manure is produced as a side product during the biogas production.


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39. Explain the two stages in the biogas production process. [3 Marks]

Ans: Biogas production process: Production of biogas is an anaerobic process.

It takes place in two stages. i. Production of acids: The microbes act on the biodegradable

complex organic compounds and produce organic acids such as acetic acid.

ii. Methane gas production: The methanogenic bacteria act on the

organic acids to produce methane gas. *1. Graphite is a conductor of electricity. Ans: i. In each layer of graphite, free electrons

move continuously within the entire layer.

ii. These electrons can conduct electricity. Hence, graphite is a good conductor of

electricity. *2. Graphite is not used in ornaments. Ans: i. The property that is used in making

ornaments and jewellery is transparency of substance and reflection of light which graphite does not possess.

ii. Also, graphite is soft, black, brittle and opaque unlike diamond, which is transparent, hard and reflects light.

Hence, graphite is not used for making ornaments.

*3. Limewater turns milky when CO2 is passed

through it. Ans: When carbon dioxide is passed through

limewater, it turns milky white due to the formation of white, insoluble calcium carbonate (CaCO3) which precipitates out of the solution.

*4. Biogas is an eco-friendly fuel. Ans: i. Production of biogas is an anaerobic

process, which means there is no form of combustion involved.

ii. It is considered to be a renewable resource as it is produced from organic waste materials.

iii. Also, there is less emission of CO2 to the atmosphere as compared to fossil fuels.

Hence, biogas is an eco-friendly fuel. 1. Intext Question. (Textbook page no. 146) i. Write down the equation of the chemical

reaction taking place between water and carbon dioxide in the experiment mentioned on textbook page no. 145.

[1 Mark] Ans: The chemical reaction taking place between

water and carbon dioxide is as follows: ii. Write down the equation of the chemical

reaction taking place on putting limewater in the gas jar of CO2. [1 Mark]

Ans: The chemical reaction taking place on putting limewater in the gas jar of CO2 is as follows:

2. Complete the following chemical reactions. *i. ……. + ……. CO2 + 2H2O + Heat *ii. ……. + ……. CH3Cl + HCl *iii. 2NaOH + CO2 ……. + ……. iv. ……. In presence of bacteria CH4 + CO2 v. 2NaHCO3

+ H2SO4 ……. + ……. + 2CO2

[1 Mark each] Ans: i. ii. iii. iv. v.

Give balanced chemical equation

2NaOH + CO2 Na2CO3 + H2OSodium

hydroxideCarbon dioxide

Sodium carbonate

WaterCa(OH)2(aq) + CO2(g) CaCO3(s) + H2O(l)

Calcium carbonate(White precipitate)

Carbon dioxide

Limewater Water

Carbonic acidWater Carbon dioxide

H2O(l) + CO2(g) H2CO3(aq)

CH4 + Cl2 Light CH3Cl + HCl

Methyl chloride

Methane Chlorine Hydrochloricacid

Acetic acid Methane Carbon dioxide

CH3COOH In presence of bacteria CH4 + CO2

2NaHCO3 + H2SO4 Na2SO4 + 2H2O + 2CO2Dilute

sulphuricacid

Sodium sulphate


Sodium bicarbonate

MethaneCH3COOH CH4 + CO2Acetic acid Carbon

dioxide

CH4 + 2O2 CO2 + 2H2O + Heat Carbon dioxide

Methane Oxygen Water

Give reasons [2 Marks each]

Ca(OH)2(aq) + CO2(g) CaCO3(s) + H2O(l)WaterCalcium

carbonate (White precipitate)

Carbon dioxide

Calcium hydroxide

(Limewater)


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*1. Explain the difference between diamond

and graphite. Ans:

Diamond Graphite i. Diamond is a hard,

crystalline substance. Graphite is a soft, black and brittle crystalline substance.

ii. Each carbon atom is bonded to four other neighbouring carbon atoms by covalent bonds.

Each carbon atom is bonded to three other neighbouring carbon atoms by covalent bonds.

iii. It has a rigid tetragonal three dimensional structure.

It has a hexagonal layered structure.

iv. There are no free electrons in diamond.

There are free electrons in graphite.

v. It is a bad conductor of electricity.

It is a good conductor of electricity.

*2. Explain the difference between crystalline and non-crystalline forms of carbon.

Ans:

Crystalline forms of carbon

Non-crystalline forms of carbon

i. A crystalline form has a regular and definite arrangement of carbon atoms.

An amorphous / non-crystalline form has an irregular arrangement of carbon atoms.

ii. They have high and sharp melting and boiling points.

They melt over a large range of temperature.

iii. They have a definite geometrical shape, sharp edges and plane surfaces.

They do not have a definite geometrical shape.

iv. The crystalline forms of carbon are diamond, graphite and fullerene.

The non-crystalline forms of carbon are coal, coke, charcoal, etc.

1. Complete the following table: [3 Marks]

Hydrocarbon Structure Number of carbon atoms

Number of hydrogen atoms Type

Propyne - 3 4 Unsaturated hydrocarbon - H2C = CH2 2 4 -

Propane - 3 - - Ans:

Hydrocarbon Structure Number of carbon atoms

Number of hydrogen atoms Type

Propyne CH3 – C CH 3 4 Unsaturated hydrocarbon Ethene H2C = CH2 2 4 Unsaturated hydrocarbon Propane CH3 – CH2 – CH3 3 8 Saturated hydrocarbon

1. The given diagram represents the internal structure of fire

extinguisher. Answer the following questions, based on the diagram.

i. Identify chemicals A and B. ii. Name the gas released when ‘A’ comes in contact with ‘B’. iii. Give the balanced chemical equation for the reaction of ‘A’

with ‘B’. [3 Marks]

Ans: i. A is sulphuric acid and B is sodium bicarbonate powder. ii. Carbon dioxide (CO2) iii.

Complete the given chart/table

Questions based on diagram

2NaHCO3 + H2SO4 Na2SO4 + 2H2O + 2CO2Dilute

sulphuricacid

Sodium sulphate


Sodium bicarbonate

The knob

Capsule

A

B

Distinguish between [2 Marks each]


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2. Observe the following diagram and answer the questions given below: i. What does the above given diagram represent? ii. What are the major gases produced, which can be collected through the exit? iii. Mention the use of the spent slurry produced in this process.

[3 Marks] Ans: i. The above given diagram represents a biogas plant. ii. The major gases produced in a biogas plant, which can be collected through the exit, are methane and

carbon dioxide. iii. The side product (spent slurry) produced in this process is used as manure for plants. 1. Two carbon compounds ‘P’ and ‘Q’ have

molecular mass 16 u and 44 u respectively. Both are colourless gases at room temperature. ‘P’ is used as a domestic fuel. ‘Q’ in liquefied form is used to remove caffeine from coffee. ‘P’ and chlorine gas react with each other at 250-400C in presence of ultraviolet light to form ‘R’ and hydrogen chloride.

Based on the above paragraph, answer the following questions.

i. Write the molecular formulae of ‘P’ and ‘Q’. ii. Explain the solubility of ‘P’ in water. iii. Write the chemical equation for the

complete combustion of ‘P’. iv. Name the compound ‘R’. v. Mention any two uses of ‘Q’ other than

the one mentioned in the given paragraph. Ans: i. ‘P’ is CH4 and ‘Q’ is CO2. ii. Methane (P) is sparingly soluble in

water. iii.

iv. Compound ‘R’ is methyl chloride (or chloromethane).

v. Refer Answer the following: Q.30.

1. Try this. (Textbook page no. 138) i. Take some milk in an evaporating dish.

Heat the evaporating dish on a Bunsen burner. What remains behind at the bottom of an evaporating dish on complete evaporation of the milk?

Ans: On complete evaporation of milk, a charred black substance remains behind at the bottom of the evaporating dish.

ii. Take small samples of sugar, wool, dry

leaves, hair, seeds, split pulses and plastic in separate test tubes. Heat each test tube and observe the changes taking place in the substances. What does the black substance remaining in each test tube indicate?

Ans: On heating each test tube, a black substance remains behind in each one of them indicating the presence of carbon.

2. Intext Question. (Textbook page no. 138) Make a list of all substances/objects that

you use in daily life from morning till night and divide those substances into the columns in the following table.

Metallic objects

Earthen / glass objects

Other objects / substances

Apply your Knowledge Questions based on paragraph [5 Marks]

CH4 + 2O2 CO2 + 2H2O + Heat Carbon dioxide

Methane Oxygen Water

Exit of gas

Slab cover Overflow tankMixing tank

(Slurry of cattle dung)

Dung and Water mixture

Outlet chamber

Inlet chamber

Undergrounddigester tank

Spentslurry


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Ans: Metallic objects

Earthen / glass objects

Other objects /

substances Cutlery, jewellery, keys, knives, chains, boilers, taps, batteries, etc.

Earthen objects: pottery, handicrafts, lamps, etc. Glass objects: Windows, cutlery, bottles, jars, etc.

Foodstuffs, fuels, medicines, clothes, plastics, wooden objects-chairs, tables, etc.

[Note: Students can find out more substances/objects and add to the above list.] 3. Try this. (Textbook page no. 141) Apparatus: Lead pencil, electrical wires,

battery/cell, small bulb, water, kerosene, test tubes, etc.

Procedure: i. Remove the lead from a pencil, and feel

it with your fingers. What colour is it? Try to break the lead with your hand.

ii. Assemble the apparatus as shown in the diagram. Start the electric current in the circuit. Observe. What did you find?

iii. Take some water in a test tube. Take

some kerosene in another test tube. Put lead dust in both the test tubes. What did you find?

Ans: i. The colour of lead from pencil is black. It can be easily broken as it is brittle and soft.

ii. When electric current is passed through the circuit as shown in the diagram, the bulb glows as graphite is a good conductor of electricity.

iii. Lead dust (graphite) forms a suspension, which means that it is insoluble in both water and kerosene (organic solvent).

4. i. Try this. (Textbook page no. 143) Apparatus : 3 conical flasks, stirrer. Chemicals : Water, kerosene, cooking oil,

coal powder, etc. Procedure : Take 3 conical flasks and take

cooking oil, water and kerosene respectively

in each. Add half a spoonful of coal powder in each of the conical flasks and stir with the help of stirrer. Observe the mixtures in the three conical flasks.

Ans: The mixtures in the three conical flasks have non-uniform composition (i.e., they form heterogeneous mixtures) as coal powder remains as it is in these solvents.

ii. Use your brain power!

(Textbook page no. 144) a. In which of the solvents- water,

kerosene and cooking oil does the coal powder dissolve?

b. What inference will you draw about the solubility of carbon?

Ans: a. Coal powder does not dissolve in these solvents.

b. Carbon does not dissolve in water and organic solvents.

5. Try this. (Textbook page no. 144) Apparatus: Coal, match box, moist litmus

paper, etc. Procedure: Ignite the coal. Hold the moist

blue litmus paper over the gas released on igniting the coal.

Note the observation. i. With which gas in the air does the

coal react on igniting? ii. What is the substance formed? iii. What change takes place in the litmus

paper? iv. Write down the chemical reaction

taking place in the above procedure. Ans: i. On ignition, the coal (carbon) reacts

with oxygen in the air. ii. Carbon dioxide (CO2) is formed on the

reaction of coal with oxygen. iii. The moist litmus paper turns from blue

to red in colour.

Flow of electric current through graphite

Pencil

Bulb

Cell

Reaction of carbon with oxygen

Coal

Moist blue litmus


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iv. The chemical reaction taking place in the above procedure is:

6. Intext Question. (Textbook page no. 144) Apparatus: Test tube, straw, limewater,

etc. Procedure: Take freshly prepared limewater in a test tube. Blow for sometime into the limewater through the straw and observe the limewater.

i. What did you see? ii. What might be the reason behind the

change? Ans: i. On blowing through the straw into the

limewater, the limewater turns milky white.

ii. Carbon dioxide (CO2) from the exhaled air turns the limewater milky white due to the formation of insoluble calcium carbonate (CaCO3).

7. Try this. (Textbook page no. 144-145) Apparatus: Retort stand, round bottom

flask, thistle funnel, gas delivery tube, gas jars.

Chemicals: Calcium carbonate (Pieces of Shahabad tiles/marble pieces/ limestone), dilute hydrochloric acid.

Procedure: i. Assemble the apparatus as shown in

the figure. While assembling, place CaCO3 in the round bottom flask.

ii. Add dilute HCl in the flask through thistle funnel. See to it that the end of the funnel dips in the acid.

iii. CO2 is formed as a result of the reaction between CaCO3 and HCl. Collect this gas in four to five gas jars.

The chemical equation of the above reaction is as follows.

Study the physical and chemical properties

of carbon dioxide. i. Observe the colour of the gas formed in

the above experiment. ii. Smell the gas in the gas jar. Use separate gas jars for the activities (iii)

to (vii) given below: iii. Remove the lid of a gas jar and put

some limewater in it. iv. Place a burning candle in a gas jar. v. Drop a small amount of a solution of

some universal indicator in one gas jar filled with CO2 and shake it.

vi. Pour some water in a gas jar and shake it. vii. Moisten a blue and a red litmus paper

and drop them in a gas jar of CO2. Enter your observations in all the above activities in the following table. Physical properties of CO2

Test Observations Odour Colour

Chemical properties of CO2

Test Observations Burning candle Universal indicator Limewater Water Litmus paper

Ans: Physical properties of CO2:

Test Observations Odour CO2 is odourless Colour CO2 is colourless

Reaction of limewater with CO2

Limewater

Blowing air

CaCO3 + 2HCl CaCl2 + H2O + CO2Calcium

carbonate Hydrochloric

acid Calciumchloride


Preparation of carbon dioxide

Dilute hydrochloric acid

CaCO3 CO2 Upward displacementof air

Thistle funnel

Carbon Oxygen Carbon dioxide

C(s) + O2(g) CO2(g)

Ca(OH)2(aq) + CO2(g) CaCO3(s) + H2O(l) Limewater Carbon

dioxide

Calcium carbonate

Water


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Chemical properties of CO2:

Test Observations Burning candle

CO2 will extinguish the flame of the candle.

Universal indicator

CO2 turns the solution of universal indicator to yellow/orange.

Limewater CO2 turns limewater milky. Water CO2 sparingly dissolves in

water forming carbonic acid (H2CO3).

Litmus paper CO2 turns moist blue litmus paper to red whereas moist red litmus paper remains as it is.

8. Intext Question. (Textbook page no. 146) Nowadays, many types of fire extinguishers

are used. Collect more information about the way CO2 is used in them to extinguish a fire.

(Students are expected to collect more information about CO2 based fire extinguishers on their own.)

9. Intext Question. (Textbook page no. 148) Using ICT.

Prepare a detailed report on carbon. Use computer applications such as Notepad, Word for this purpose and send the reports to others. Websites: https://www.boundless.com/chemistry/, www.rsc.org/learn-chemistry

(Students are expected to prepare a report on their own using the above mentioned websites.)

10. Find out. (Textbook page no. 148)

Visit a biogas plant and get to know the actual functioning of the plant. Find out which electrical instruments are run on that plant.

Ans: Working of biogas plant: The steps involved in the working of a biogas

plant are as follows: i. Biogas is made in a biogas digester. ii. All types of wet organic wastes are

mixed with an equal quantity of water in the mixing tank, which is present above the ground level. This forms the slurry.

iii. The digester, which is a well-like structure, present underground, is partially filled with slurry and left unused for about two months.

iv. During this period, anaerobic bacteria present in the slurry decompose the biomass in the presence of water.

v. As a result, biogas is formed which starts collecting in the dome of the digester and as more and more biogas starts collecting, it exerts pressure and forces the spent slurry into the outlet chamber.

vi. This spent slurry is removed manually and used as manure for plants.

vii. To obtain a continuous supply of biogas, a functioning plant can be fed continuously with the prepared slurry.

Some electrical instruments that can run on biogas include,

i. Solar water heaters ii. Electric generators iii. Hot water boilers iv. Gas turbines, etc. [Note: Students can find out additional information

by visiting a biogas plant.] 11. Complete the following crossword: Down 1. The amorphous form of carbon, which

is used in the production of water gas and producer gas.

2. The crystalline form of carbon, which is a bad conductor of electricity.

5. The gas, which contains 55 to 60% methane and the rest of the constituent as carbon dioxide.

Across 3. The crystalline form of carbon whose

one layer is called graphene. 4. The gas, which is also known as marsh gas. 6. The type of coal, which is formed in the

second step of the formation of coal.

1

2

3

4

5

6


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Ans:

*12. Project. Make a model of a biogas plant and make a

presentation in the class about the process of gas production.

(Students are expected to prepare the model for biogas plant and make a presentation.)

G R A P H I T E

D

A

M

O

ND

O

C

K

E T H A EN

L I G I T E

B

O

G

A

S

1

2

3

4

5

6

Memory Maps

Hydrocarbons containing at least one double or triple bond between carbon atoms. Example: Ethene (CH2 = CH2), Ethyne (CH = CH), etc.

Unsaturated hydrocarbons

Compounds containing carbon and hydrogen

Hydrocarbons

Hydrocarbons containing only single bond between carbon atoms. Example: Methane (CH4), Ethane (CH3–CH3), etc.

Saturated hydrocarbons

Crystalline forms

It consists of 30-900 carbon atoms.

They include buckyballs and buckytubes.

Fullerenes

It has a hexagonallayered structure.

Opaque, soft and brittle

Graphite

It has a tetragonal 3-D structure.

Transparent and hard

Diamond Coal Charcoal

Peat Contains less than 60% of carbon

Lignite Contains 60-70 % of carbon

Bituminous coal

Contains 70-90 % of carbon

Anthracite Contains 95 %of carbon

Carbon

Non-crystalline forms

Coke


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[Total Marks: 25] Q.1. (A) Answer the following. [5] i. Fill in the blank. The organic compound, urea was prepared from _______ by German chemist Wohler. ii. Identify the odd one out and justify. Coal, coke, charcoal, graphite iii. Right or wrong. If wrong, write the correct sentence. Propane is an unsaturated hydrocarbon. iv. Match the hydrocarbons with the type of carbon-carbon bond present in them:

Hydrocarbon Carbon-carbon bond a. Ethene 1. Single bond b. Ethyne 2. Double bond 3. Triple bond

v. Complete the analogy and explain. Limestone : CaCO3 : : Calamine : _______. (B) Choose the correct alternative. [3] i. Dilute hydrochloric acid is added to pieces of Shahabad tiles taken in a round bottom flask. It

is observed that _______. (A) the solution turns black (B) a brisk effervescence occurs (C) the solution turns milky (D) a loud sound is produced ii. Nikita tests carbon dioxide gas with moist litmus paper. She observes that _______. (A) red litmus turns blue (B) blue litmus turns red (C) blue litmus remains as it is (D) red litmus paper turns green iii. Carbon dioxide gas _______. (A) supports combustion (B) is neutral in nature (C) has sweet smell (D) is colourless Q.2. Answer the following (any three). [6] i. How does a modern CO2 based fire extinguisher work? ii. Give four examples of hydrocarbons. iii. Explain the chlorination of methane with chemical equation.

iv. What happens when CO2 is passed through limewater? Give chemical equation.

Chapter Assessment


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Q.3. Answer the following (any two). [6] i. Study the following diagram and answer the questions given below: a. What does the above figure represent? b. What are the valencies of carbon and hydrogen? c. How many C-H bonds are formed in the given molecule? ii. Answer the following questions based on the given diagram. a. Name the type of chemical bond formed between the carbon atoms. b. Identify the product formed when the above substance is heated at 800C in the

presence of oxygen. c. Give two uses of the above substance. iii. Complete the following:

a. 2NaOH + CO2 +

b. CH4 + 2O2 + + Heat

c. Na2CO3 + H2O + CO2

d. H2O + CO2 Q.4. Answer the following (any one). [5] i. With the help of a concept map, explain the different crystalline and non-crystalline forms of

carbon. ii. Describe an experiment to prove that graphite is a good conductor of electricity. Q.1. (A) i. ammonium cyanate ii. Graphite, Graphite is a crystalline form of carbon while others are non-crystalline forms of carbon. iii. Wrong, Propane is a saturated hydrocarbon. iv. (a – 2), (b – 3) v. ZnCO3, The molecular formula of limestone (calcium carbonate) is CaCO3. Similarly, the molecular

formula of calamine (zinc carbonate) is ZnCO3.

Answers

Carbon

H

CH H

H

Target Pub_Std IX Science and Technology (English Medium)_Text.pdf 244 2/14/2018 10:56:42 AM

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(B) i. (B) ii. (B) iii. (D) Q.2. i. In modern fire extinguishers, liquid and solid CO2 is filled under pressure. On reducing the

pressure, it turns into gaseous state and comes out forcefully through the horn-like hose pipe. ii. Methane (CH4), Ethane (H3C – CH3), propene (CH3 – CH = CH2), propyne (CH3 – C CH) iii. Methane and chlorine gases react with each other at the temperature of 250 C to 400 C in

presence of ultraviolet light and form mainly methyl chloride (chloromethane) and hydrogen chloride. This reaction is called chlorination of methane.

Chemical reaction: iv. Refer Give reasons: Q.3. Q.3. i. a. The above figure represents electron dot model of methane. b. The valencies of carbon and hydrogen are 4 and 1 respectively. c. In methane molecule, four C-H bonds are formed. ii. a. Covalent bond b. When diamond is heated at 800C in the presence of oxygen, carbon dioxide (CO2) is

formed. c. Refer Answer the following: Q.18.i. iii.

a. 2NaOH + CO2 Na2CO3 + H2O

b. CH4 + 2O2 CO2 + 2H2O + Heat

c. Na2CO3 + H2O + CO2 2NaHCO3

d. H2O + CO2 H2CO3 Q.4. i. Refer Answer the following: Q.12. and Memory maps. ii. Refer Answer the following: Q.10.

CH4 + Cl2 Light CH3Cl + HCl

Methane Chlorine Methyl chloride

Hydrogenchloride


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